1. Field of the Invention
The present invention generally relates to vacuum filament displays and more particularly to a drive circuit for a vacuum filament display.
2. Description of the Related Technology
It is known in the prior art to provide a control device with a microcomputer unit, a vacuum fluorescent display having a filament, a set frequency power supply interconnected to a high voltage alternating current power supply, and connecting circuit, as shown in U.S. Pat. No. 5,365,146, the disclosure of which is expressly incorporated by reference herein. The arrangement includes a power supply creating a low voltage direct current to power the microcomputer unit, the filament is connected to a capacitor so that a direct current is pulsed through the filament at the same frequency as the certain frequency of the high voltage alternating current power supply (50-60 Hz) so as to heat the filament to an operating temperature.
It is also known to utilize a pair of transistors each having a base emitter junction and connected in parallel together with an oscillator transistor connected between the base emitter junctions of the transistors and one side of the capacitor so that the oscillator transistor will cause the transistors to be turned off and on at a certain frequency to provide an oscillator unit.
It is also known in the prior art to provide a control device with a microcomputer unit, a vacuum fluorescent display having a filament, a power supply interconnected to a high voltage alternating current power supply that has a certain frequency, and a circuit operatively interconnecting the elements together. The power supply includes a transformerless capacitor arrangement for creating a low voltage direct current from the power supply to power the microcomputer, the circuitry including an oscillator that receives the pulses direct current through the filament at a frequency that is greater than the certain frequency and that causes the filament to heat to an operating temperature.
It is also known to utilize a secondary winding on a transformer to drive a vacuum filament display.